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| Titel |
Ion distributions upstream of an interplanetary shock |
| VerfasserIn |
Primoz Kajdic, Heli Hietala, Xochitl Blanco-Cano |
| Konferenz |
EGU General Assembly 2017
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| Medientyp |
Artikel
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| Sprache |
en
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 19 (2017) |
| Datensatznummer |
250146962
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| Publikation (Nr.) |
 EGU/EGU2017-11036.pdf |
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| Zusammenfassung |
| It is well known that supercritical collisionless shocks in the interplanetary (IP) space reflect
part of the incoming particles (ions, electrons) in order to dissipate the kinetic energy of the
upstream solar wind flow. When the conditions are right the reflected particles can escape far
upstream from the shock. Their interaction with incoming ions and electrons results in the
formation of the foreshock region which is populated by ultra-low frequency magnetic
field fluctuations and different populations of reflected ions. Our knowledge on the
latter comes mostly from observations of our planet’s foreshock. However, the bow
shock of the Earth typically has high Mach numbers, and the relatively small global
curvature radius of the shock’s shape affects the ion distribution characteristics.
Interplanetary (IP) shocks, on the other hand, typically have lower Mach numbers and larger
global curvature radii. In the past the majority of observed ion distributions detected
upstream of IP shocks were diffuse. In only a couple of works the field-aligned ion
beams were reported and even then the details of the ion distributions functions
could not be determined. Here we present the first study showing clear observations
of different types of ion distributions upstream of an interplanetary shock. The
shock was observed on 8 October 2013 by several spacecraft, namely Wind, ACE,
and the two ARTEMIS spacecraft P1 and P2. By using combined data from the
Electrostatic Analyzer and the Solid State Telescope instruments onboard both ARTEMIS
spacecraft we observed different types of ion distributions upstream of the shock: The
distributions changed from field-aligned ion beams that were detected farthest from the
shock, to intermediate and then to almost diffuse ion distributions near the shock
transition. Furthermore, the observations at P1 and P2 locations also show spatial
variability of the foreshock and the IP shock. The angle between the local shock normal
and the upstream magnetic field, θBn, was larger at P1 where the upstream ion
fluxes were somewhat weaker than at P2 which observed the shock with smaller
θBn. |
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